With less than two weeks to go before the November 6 presidential election, things are getting heated out there on social-media sites like Twitter and Facebook.

Twitter said that Monday’s third presidential debate generated 6.5 million tweets, on top of the 21 million churned out during the previous debates (two presidential and one vice presidential). Most of that activity was harmless — partisans supporting their candidate or taunting the opponent, remarking on hot memes like Big Bird or binders full of women, noting interesting exchanges, and more.

But according to the Los Angeles Times, some people tweeting during the debates had more ominous messages: death threats against either President Barack Obama or his challenger, former Massachusetts Gov. Mitt Romney. And the U.S. Secret Service is not blind to these threatening — and illegal — tweets.